The Q&A Archives: Avalanche Evergreen Clematis

Question: Early this spring I bought a specimen of Clematis x cartmanii 'Blaaval'. Up until recently it appeared to be flourishing. I got an 'avalanche' of white flowers and then a period of healthy green growth. Now large portions of the plant are wilting. I have increased watering but to no avail. The wilted leaves do not recover, even in the early morning and evening, when it is no longer hot. I live at 6000 feet in the San Jacinto Mountains, above Palm Desert. I am an experienced gardener and the clemetis has its feet in the shade. I fed a 30-10-10 water soluble acid fertilizer about 2 weeks ago, soaking the soil.
Thank you, Eddie

Answer: Since you're an experienced gardener, I'm sure you've investigated the usual causes of wilting in plants so I won't go into details, but have you considered Clematis wilt (Phoma clematidina)? This is a dreaded disease of clematis and the symptoms are fairly easy to recognize: One or more shoots wilt and die rapidly, starting at the shoot tip or a leaf and spreading downwards, even as far as the base. The leaf stalks blacken when infection spreads from the blade and freshly infected stems blacken internally.

Some large-flowered cultivars are particularly suscepible. Smaller-flowered species such as Clematis montana are generally resistant.

Wilting can also be caused by waterlogging, graft failure, insect or slug damage. However the symptoms are not as localized, and other symptoms do not appear.

Clematis wilt disease is caused by the fungus Phoma clematidina. Spores are spread by water splash. The fungus can remain in the soil for many months in old infected plant tissue. To control, cut back the wilted shoots to healthy tissue. This may mean pruning below the soil surface. Your plant may not show the same symptoms next year - I certainly hope it doesn't! Best wishes with your clematis!

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